The basic mechanical skills of the visual system are: eye movements, which are important for following a moving object or looking from one object to another, as well as the ability to look at a single object, whether still or moving, for as long as is necessary; eye teaming, which refers to both eyes pointing at the same thing at the same time; without this ability there can be confusion and disorientation in processing visual information for meaning and response; and focusing, which is the ability to see clearly at any distance for any period of time with minimal effort. Other very important aspects of visual function are peripheral visual awareness and eye/hand coordination.
Normal visual acuity, which we know as 20/20, is the ability to recognize a certain size letter at a certain distance. While this is typically the main focus (pun unavoidable) of most eye exams; in the overall scheme of visual performance it is not nearly as important as we are led to believe. Many people with 20/20 eyesight have inadequate visual skills, leading to functional vision problems that seriously hinder, or prevent high-level performance.
Peripheral visual awareness is the foundation on which all visual skills and performance are built. Peripheral vision guides the eyes in locating precisely where they both should aim; this in turn allows the eyes to move smoothly together from one place to another as well as giving information on where to focus so the object will be clear. If all of this is not working smoothly and automatically, a number of problems are likely to result. Decreased visual function can lead to difficulty with reading, handwriting, and copying from the board as well as reduced attention span, hyperactivity, fatigue, poor coordination, headaches and some types of motion sickness. Good visual skills are also important for safe, effective driving even though the only visual ability tested for a driver's license is distance visual acuity.
Eye Movements: Tracking is the ability to visually follow a moving target or switch attention from one object to another. Fixation is the ability to look directly and steadily at a specific object. These skills permit easy shifting of the eyes along the line of print in a book, a rapid and accurate return to the next line, and quick, accurate shifts between desk and chalkboard. Inadequate eye movement control may cause loss of place when reading, difficulty copying from the chalkboard, and skipping or omitting letters or small words when reading.
Focusing is another skill that is important for school performance. This skill allows rapid and accurate clarity as we look from one distance to another such as from desk to chalkboard. It also permits clear focus at the normal reading distance for appropriate periods of time. Signs of a focusing problem may include blurred vision, fatigue or headaches while reading, and inability to see clearly at distance after reading. This may lead to a form of nearsightedness that is preventable or correctable if properly diagnosed.
Eye Teaming is important in order to have comfortable vision. If the two eyes do not work together in a very precise and coordinated fashion, it can result in double vision (which often goes unreported). There are several different types of eye teaming problems that can occur. In one common form, one eye may be seen turning in or out intermittently or even all of the time; the technical term for this is strabismus. Another common occurrence, especially with strabismus, is for the image from one eye to be ignored by the brain because the images from the two eyes do not match well enough to combine into a single image, which may lead to what is known as a “lazy eye” (amblyopia). Most eye turns that disrupt efficient visual performance can go undetected without specialized testing because they are not cosmetically noticeable. Poor eye teaming can result in frequent loss of place when reading, words appearing to move on the page, poor handwriting, headaches or eyestrain. There will usually be an inability to stay at a visual task for any prolonged period of time. Poor eye teaming can also result in poor depth perception. This may contribute to motion sickness and poor general coordination, which can lead to dissatisfaction with, or avoidance of, sports activities.
Peripheral awareness is the capacity to be aware of, but not distracted by, the total visual environment while engaged in any specific task. It is the foundation of all the previously mentioned visual abilities. Peripheral vision can be significantly reduced by stress, causing a reduction in visual information processing. This stress response tends to continue even after the visual demand has ended and may become chronic. Sports performance, often an important aspect of social acceptance for the school-aged child, can be compromised by poor peripheral awareness. Signs of reduced peripheral efficiency include distractibility, decreased attention span, hyperactivity, and poor comprehension. Activities such as reading, writing, and copying from the board can also be adversely effected, as well as general coordination.
Eye/hand coordination refers to the ease and accuracy with which our eyes guide our hands to write, draw, make things, pour things, catch a ball, etc. While we typically think of our hands being responsible for such activities, it is really the eyes that are required to lead the hands into action. If the eyes are not accurately informing the hands, we cannot efficiently perform these types of activities.
Within a few years of birth our visual system must somehow be ready for learning to read. This is a fairly simple process for most of us. Significant problems often arise in a few more years when we must begin reading to learn. This is a much more complex process that requires effortless, comfortable visual performance especially in the areas of eye movements, focusing, eye teaming and peripheral vision. If the visual system is not working automatically it drains energy, which would otherwise be used for attending to, comprehending, and making use of visual information. The relationship between vision and learning is complex. We must be able to both keep our eyes still for periods of time and to move our eyes quickly and accurately from place to place countless times throughout the school day. We must be able to maintain clear focus for periods of time to investigate details and we must be able to shift focus quickly and accurately from one point to another countless times throughout the school day. We must be able to use our eyes effortlessly as a team at all times so that there is a normal 3-dimensional appearance to the world and good ability to judge distances and depth.
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